The instant invention relates to biocidal coating compositions, particularly paints, in which hydrated lime is used as a biocidal agent and a method of making certain such compositions and paints more particularly, the present invention relates to a method for increasing the shelf life of such compositions.
Hydrated lime is well known as a disinfectant, biocidal, and biostatic agent its effectiveness for these purposes is based on its high alkalinity, a pH above about 11, in order to retain its biocidal activity after application to a desired surface, a hydrated lime must retain the high alkalinity necessary to kill microorganisms.
Unfortunately, hydrated lime is highly susceptible to environmental attack, primarily by carbon dioxide present in the ambient atmosphere. Carbon dioxide converts the hydrated lime to calcium carbonate, which does not have the alkalinity required to kill microorganisms. Such a consequence has mitigated against the use of hydrated lime in coating compositions, such as paints and whitewash, as effective long term disinfectants, biocides, or biostatic agents.
The prior U.S. Pat. Nos. 6,280,509, 6,231,650 and 6,042,638, whose entire disclosures are hereby specifically incorporated by reference, disclose coating compositions which have overcome this problem and are effective coatings that resist degradation by carbon dioxide for prolonged periods of time. Such compositions, however, may not be truly washable or cleanable with aqueous materials and their use is thereby limited. Also, it was not possible to use with such compositions the conventional latex vehicles used in forming paints which employanionic or cationic surfactants and emulsifiers.
Most interior building paints are based on a latex vehicle and their popularity results from their easy application, low odor, good appearance, and ability to be cleaned with soap and water.
As noted in the prior parent applications, such conventional latex binders were incompatible with hydrated lime which results in coagulation and phase separation almost immediately upon blending with lime.
The present invention provides a method and composition for aforementioned paints which allows the paints to have greater shelf life and reduces the hardening, thickening and cross linking of the paints during their useful life.